The invention relates to a method and a device for extracting fumes and heat in the event of a fire by the locally selective exhaustion of fumes, as well as the ventilation in event of xe2x80x9cheavy trafficxe2x80x9d or xe2x80x9cpoor air qualityxe2x80x9d by the exhaustion of pollutant-laden air or by the selective supply of fresh air for traffic structures and spaces.
In case of fires in traffic spaces, such as tunnels, it must be ensured that, for a certain period of time, the visibility does not deteriorate due to the fumes and plume gases evolved to such an extent, that the intended flight paths can no longer be recognized reliably or utilized safely and, because of high temperatures, poisonous gases and a detonation of incompletely combusted gases, people in the traffic space, the safety facilities or the structure itself are endangered.
The previously used fume-extraction facilities in traffic structures and enclosed spaces (see EP 0428 108 A2) basically have the advantage that, on the one hand, the visibility necessary for rescuing persons and objects is improved and, on the other, the temperatures are significantly lower and the amounts of fumes significantly less in the vicinity of the fire than in the absence of fume-extraction facilities.
For enclosed spaces, the fume-extraction facilities of DIN 18 232 (part 1 to part 3) can be projected in such a manner, that free visibility up to a certain height is ensured for an assumed fire load. In general, for various reasons, this procedure is not possible for traffic structures.
For traffic structures, such as tunnels, different concepts are known for meeting the fire protection requirements and adhering to visibility conditions. Essentially, there are two different methods.
In the event of a fire in a tunnel, a vigorous longitudinal ventilation, for example, over large jet ventilators, is produced in such a manner that the windward side of the fire is kept free of smoke in every case (no back-layering of the fumes). The axial flow velocities in the tunnel, required for this purpose, are known and range from 4 to 6 m/s. However, at these flow velocities, the lee side of the fire is filled completely with smoke and can no longer be used as a flight path.
The second method comprises the extraction of fumes over special fume-extraction ducts, which are disposed over the whole length of the tunnel. Either fumes are extracted uniformly over all existing openings in the fume-extraction duct (multi-point system) or, of the fire covers, which are distributed uniformly in the whole of the smoke-extraction duct, only those in the vicinity of the fire are opened. Over the latter, the fire gases can then be extracted (single-point system). The single-point extraction has generally turned out to be the more efficient method.
In all known cases of fume-extraction facilities, pipe ventilators (portal ventilators) are used to extract fumes and are generally mounted centrally to the outlet of the fume-extraction ducts, (portal or chimney) (for example, EP 0428 105 A2). These facilities can partly also be used for the operational ventilation, either by extracting pollutant-laden air (semi-transverse ventilation by outgoing air) or by supplying fresh air (semi-transverse ventilation by incoming air), in that the portal ventilators are reversed.
The essential disadvantage of all known arrangements for extracting fumes is the following. On the one hand, a reduced pressure must be built up, to begin with, by the portal ventilator (pipe ventilator), which is at the end of the extraction system, so that the fire gases can be extracted through the openings (fire covers) into the fume-extraction duct. The greatest pressure difference exists directly at the pipe ventilator and the least pressure difference exists at the opening, through which the fumes are to be extracted. In the case of longer distances, such as in tunnels, the time required to build up the necessary reduced pressure can amount to a few minutes. On the other hand, in the case of a single-point system, it must be assumed that all fire covers of the whole of the fume-extraction duct, which are not in the vicinity of the fire, are pressure-tight. In the event of leakages or if fire covers have been opened wrongly, the effectiveness of the pipe ventilator and, with that, the extraction performance are reduced. This can lead to a total failure of the system in the event of a fire. Furthermore, components and facilities, in the vicinity of the fire, including the extraction duct and the portal valves can themselves be involved as a result of the high temperatures of the fire. In the case of fires in the vicinity of the portal ventilators, the latter are no longer capable of functioning because of the high temperatures at the pipe ventilators. Moreover, two portal ventilators are generally used, resulting in twice the installed performance, in order to increase the safety (redundancy) of the system.
If some of the fumes extracted are combusted incompletely and mixed at a high temperature with fresh air in the fume-extraction duct, there may be detonations, which destroy the fume-extraction system and, in addition, endanger persons in the traffic space.
Installations or facilities, in which the conventional fume-extraction equipment is supplemented by sprinkler equipment in the vicinity of the fire, are also known (EP 0703807 A1).
It is therefore an object of the invention to construct a fume and heat extraction device as well as operational ventilation for traffic structures and enclosed spaces, which act essentially without delay when switched on, do not become ineffective due to leakages at the fume duct, offer the parts of the device themselves (fume-extraction duct and tunnel wall) reliable protection even at high fire loads and extraction of incompletely combusted gases and realize the function of operational ventilation as semi-transverse ventilation by outgoing air, as semi-transverse ventilation by incoming air and as their combination.
Pursuant to the invention, this objective is accomplished by the distinguishing features of claims 1 and 6. Advantageous developments arise out of the dependent claims. In the following, the invention is described by means of examples illustrated in FIGS. 1 and 2a, b and c.